Question

A and b together can complete a job in 8 days.Both b and c working alone can finish the same job in 12 days.A and b commence works on the job and work for 4 days

Answer 1

A+B)'s 1-day work = 1/8
B's 1-day work = C's 1-day work = 1/12.

(A+B)'s 4-day work = 4x(1/8)  = 1/2.
remaining work = 1 - (1/2) = 1/2
B's 2-day work = 2x(1/12) = 1/6
Remaining work = (1/2) - (1/6) = 1/3
Remaining (1/3) work is to be done by C alone whose 1-day job = (1/12)
Hence No. of days C requires = (work to be done) / (C's 1-day work)
                                           = (1/3) / (1/12) = 4 Days